1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing method, a display apparatus, and a projection display apparatus for carrying out image signal correction processing, among others.
2. Description of the Related Art
There exist image processing apparatuses capable of image signal correction such as gamma correction, typically using digital circuits for multiple-point break correction as part of a correction circuit that carries out gamma correction based on a look-up table (LUT) arrangement. Apparatuses of this type are disclosed illustratively in Japanese Patent Laid-open Nos. 2001-320607 and 2004-120366.
In recent years, the LUT-based digital correction circuit has come to gain widespread acceptance because of its high accuracy of image signal correction. A typical LUT-based digital correction circuit uses as its LUT a memory having 2n addresses, “n” being the number of quantization bits in an input signal. The LUT accommodates gamma correction data corresponding to the level of the input signal. Furnished with the LUT, the correction circuit performs gamma correction by taking into account the transmittance characteristic (V-T characteristic) with regard to the applied voltage of the image display apparatus of interest.
In other words, the image display apparatus such as a liquid crystal displays establishes in its storage unit an LUT containing gray-level correction data computed in accordance with a V-T curve characteristic of the transmittance regarding the applied voltage. The display apparatus carries out gray-level correction by reading the gray-level correction data from R, G and B input signals.
The above-cited patent application No. 2004-120366 discloses a technique practiced in conjunction with an LUT divided into a first and a second memory unit. In operation, gamma correction data about two nearby points of an input signal is derived from the address corresponding to the input signal and input as designated to either of the two memory units.
The above technique involves generating gamma correction value data by executing linear interpolation based on the designated correction data and on the input signal. The memory capacity needed for table translation is reduced by performing computations to interpolate what is lacking in LUT capacity as well as in the amount of necessary data.